Control valve system for a four-speed automatic power transmission transaxle

ABSTRACT

A control valve system for a four speed automatic transmission wherein a single valve mechanism acts in combination with a 2-3 shift valve, a 3-4 shift valve and a torque sensor throttle valve to control heavy throttle 2-3 upshifts, light throttle 2-3 upshifts, light throttle 3-4 upshifts, heavy throttle 3-4 upshifts, heavy throttle 3-2 downshifts and coasting downshifts to provide maximum smoothness in the engagement and release of fluid pressure operated ratio control servos.

GENERAL DESCRIPTION OF THE INVENTION

This invention comprises improvements in a control valve system such asthat shown in copending application Ser. No. 713,356, filed Mar. 18,1985, by J. S. Vanselous, which is assigned to the assignee of thisinvention. The control circuit of this invention may be used to controlratio changes in a transaxle structure such as that shown in Vahratianet al U.S. Pat. No. 4,509,389, dated Apr. 9, 1985, which is assigned tothe assignee of this invention.

Like the control circuit shown in application Ser. No. 713,356, thedisclosure of this application relates to valve circuitry forcontrolling the application and release of clutches and brakes toestablish four forward driving ratios in the transmission structure ofU.S. Pat. No. 4,509,389. The control circuitry includes a fluid pressurepump driven by the engine for a wheeled vehicle driveline and fluidpressure operated servos for controlling the application and release offriction clutches and brakes. The transmission includes a low andintermediate brake servo and overdrive brake servo, a forward drivefriction clutch, an intermediate drive friction clutch, and a directdrive friction clutch. Separate shift valves are provided forestablishing ratio changes between the first and second ratios, betweenthe second and third ratios, and between the third and fourth ratios,the fourth ratio being an overdrive ratio.

The third speed ratio is a direct drive ratio in which torquetransferred from the turbine shaft of the converter is distributed tothe torque input side of the gearing which is conditioned for aone-to-one operating ratio. This direct drive condition is achieved asthe direct drive clutch is engaged and the intermediate speed ratiobrake is released. The intermediate speed ratio brake includes a brakeband that engages the reaction element of the gearing duringintermediate speed ratio operation, the brake band servo being dividedinto two regions identified in the disclosure as a servo brake releaseregion and a servo brake apply region. When both regions arepressurized, the intermediate speed ratio servo is released. As therelease region is exhausted, the intermediate brake band servo becomesapplied. In this respect the intermediate servo functions in a mannersimilar to the intermediate servo disclosed in U.S. Pat. No. 3,309,939,issued to Stanley L. Pierce. That patent also is assigned to theassignee of this invention.

It is common practice (as shown, for example, in the Pierce patent) tohydraulically connect the direct drive clutch with the release region ofthe intermediate servo so that when the clutch becomes applied orpressurized, the intermediate servo becomes released in synchronism withthe application of the clutch. Likewise a downshift from the directdrive to the intermediate ratio is achieved by exhausting the directclutch and the release side of the intermediate servo.

The shift valves that control the ratio changes respond to a throttlepressure, which is a measure of the torque delivered by thetransmission, and governor pressure, which is a function of the drivenspeed of the driven shaft for the transmission. Heavy throttle upshiftsthus are delayed relative to light throttle upshift because of theinfluence of the throttle pressure on the shift valves which opposes theforce applied to the shift valves by the governor pressure. Controlpressure is applied to the shift valves by a driver operated manualvalve, which permits the driver to select the various drive ranges.

In order to effect a smooth ratio change from the intermediate ratio tothe direct drive ratio under both heavy throttle conditions and lightthrottle conditions, it is necessary to provide a so-called backoutvalve which delays the application of the direct drive clutch and therelease of the intermediate servo following shifting movement of theshift valve that controls 2-3 upshifts. This is done by providing acontrolled flow restriction in the direct clutch servo and intermediatebrake servo exhaust flow path. In this manner the application of thedirect drive clutch is cushioned and its engagement is synchronized withthe release of the intermediate brake so that harshness in lightthrottle upshifts is avoided. The flow restriction provided by thebackout valve is removed or reduced during 2-3 heavy throttle upshifts.

The improvements of this invention include a backout valve that performsthe function of known backout valve arrangements such as that shown inthe Pierce U.S. Pat. No. 3,309,939 as well as Searles U.S. Pat. No.3,344,681; Searles U.S. Pat. No. 3,327,554; Pierce U.S. Pat. No.3,400,612; and Pierce et al U.S. Pat. No. 3,613,484. Each of thesepatents is assigned to the assignee of this invention. The presentinvention is distinguished from these prior art valve systems byincorporating a backout valve in combination with the shift valves insuch a way that the backout valve is capable of controlling lightthrottle 3-4 upshifts, heavy throttle 3-4 upshifts, a power-on 3-2downshift, and light throttle downshifts which force the valve circuitunder light throttle operation to downshift from the third ratio to thefirst ratio and to skip the intermediate step of downshifting from thethird ratio to the second ratio. These multiple functions have beenadded to the usual backout arrangement of the prior art systems withoutadding to the complexity of the valve circuit and without the necessityfor adding to the valve circuit unique valve elements for performing theseparate additional functions.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS

FIG. 1 shows a schematic view of the hydrokinetic torque converter andgearing arrangement for the transmission system that is capable ofembodying the improved valve circuitry of my invention.

FIG. 2 is a chart that shows the clutch and brake engagement and releasepattern for the clutches and brakes shown in FIG. 1.

FIG. 3 is a schematic representation showing the power train electroniccontrol module that is used to control the converter bypass solenoid.

FIGS. 4A, 4B, 4C and 4D collectively show the hydraulic control valvecircuitry for controlling the transmission structure of FIG. 1, eachview showing a separate section of the circuitry.

FIGS. 4E, 4F, 4G and 4H are charts showing the relationship between theengine speed-torque curve and the effective clutch and brake servopressure for any engine throttle opening.

FIG. 5 is an enlarged schematic view of the backout valve portion of thecontrol valve circuit of FIGS. 4A through 4D.

PARTICULAR DESCRIPTION OF THE VALVE CIRCUIT OF FIGS. 4A THROUGH 4D

In FIG. 1 numeral 10 designates the crankshaft of an internal combustionengine shown schematically in FIG. 3 at 12. Crankshaft 10 is connectedto the impeller 14 of a hydrokinetic torque converter 16. The converter16 includes also a bladed turbine 18 and a bladed stator 20, the latterbeing located between the torus flow outlet section of the turbine 18and the torus flow inlet section of the impeller 14. The stator 20 issupported by a stationary sleeve shaft 22 connected to the transmissionhousing shown at 24 in FIG. 3. An overrunning brake 26 is situatedbetween the bladed section of the stator 20 and the stationary sleeveshaft 22. Overrunning brake 26 permits freewheeling motion of the stator20 in the direction of rotation of the impeller, but it preventsrotation in the opposite direction.

A torque converter lockup clutch 28 is adapted to establish a drivingconnection between the impeller 14 and turbine shaft 30, the latterbeing connected to the bladed impeller 18. For a complete description ofthe mode of operation of the clutch 28, reference may be made to thepreviously identified Vahratian et al patent.

The engine crankshaft 10 is connected to a pump driveshaft 29, whichdrives a variable displacement pump 38 for the automatic transmissioncontrol system to be described with reference to FIGS. 4A through 4D.Turbine shaft 30, which is a sleeve shaft surrounding driveshaft 29,serves as a torque input shaft for a drive sprocket 32. A drivensprocket 34 is connected to torque input shaft 36 for multiple ratiogearing disposed about the output shaft axis 38. Axis 38 is parallel andlaterally offset with respect to the engine crankshaft. Drive chain 40serves as a torque transfer member that connects drivably the drivesprocket 32 with the driven sprocket 34.

The multiple ratio gearing comprises a pair of simple planetary gearunits 42 and 44 as well as a final drive planetary gear unit 46. Gearunit 42 includes ring gear 48, sun gear 50, a planetary carrier 52 andmultiple planet pinions 54 which are journalled on carrier 52 so thatthey mesh with ring gear 48 and sun gear 50.

Carrier 52 is connected directly to ring gear 56 of the planetary gearunit 44. Gear unit 44 includes also sun gear 58, planetary carrier 60and planet pinions 62 journalled on carrier 60 so that they mesh withring gear 56 and sun gear 58.

Sun gear 58 is adapted to be braked by a low and intermediate brake band64 which surrounds brake drum 66 connected to the sun gear 58. The lowand intermediate brake 64 carries the notation B₂ in FIG. 1 as well asin the chart of FIG. 2.

A reverse brake 68 selectively brakes the ring gear 56 and the carrier52 which are connected together as explained. Brake 68 in FIG. 2 carriesthe notation CL₄ in FIG. 1 as well as in the chart of FIG. 2.

Carrier 60 is connected to torque output shaft 70 for the planetarygearing. Shaft 70 is connected to sun gear 72 of the final driveplanetary gear unit 46. Gear unit 46 includes also ring gear 74 which isheld stationary by the transmission housing. Gear unit 46 includes alsocarrier 76 which journals pinions 78 that mesh with ring gear 74 and sungear 72. Carrier 76 is connected to the differential carrier of adifferential gear unit 80. The differential carrier has pinions 82journalled thereon, and these are connected drivably to the carriers 76.

Differential gear unit 80 includes also side gears 84 and 86. Each sidegear is connected to a separate torque output half-driveshaft, theoutboard ends of the driveshafts being connected to the vehicle tractionwheels. A universal joint, not shown, connects one end of each halfshaft with its associated side gear and the outboard end of that halfshaft is connected to its associated traction wheel by a seconduniversal joint, not shown.

The input sleeve shaft 36 is connected to the carrier 52 of gear unit 42through an intermediate speed ratio clutch 88. That clutch is identifiedby the symbol CL₂ in FIG. 1 as well as in the chart of FIG. 2. Sun gear50 of the gear unit 42 is connected to brake drum 90 about which ispositioned overdrive brake band 92. Brake band 92 is identified by thesymbol B₁ in FIG. 1 as well as in the chart of FIG. 2. Sun gear 50 andbrake drum 90 to which it is connected is connected to input shaft 36through forward clutch 94 and overrunning clutch 96 situated in seriesrelationship. Clutch 94 is identified by the symbol CL₁ in FIG. 1 aswell as in the chart of FIG. 2. The overrunning clutch 96 is identifiedby the symbol OWC₁ in FIG. 1 as well as in the chart of FIG. 2.

A direct drive clutch 98 and a second overrunning clutch 100, which arearranged in series relationship, connect input shaft 36 with the brakedrum 90 and the sun gear 50. The symbol CL₃ identifies the direct driveclutch in FIG. 1 as well as in the chart of FIG. 2. A second overrunningclutch is identified by the symbol OWC₂ in FIG. 1 as well as in thechart of FIG. 2.

By engaging selectively the clutches and the brakes, four forwarddriving speed ratios can be achieved as well as a single reverse speedratio. The forward clutch 94 is engaged during operation in the firstthree forward driving ratios and the intermediate clutch 88 is engagedthe second, third and fourth forward driving ratios. Direct drive clutch98 is engaged during operation in the third and fourth forward drivingratios as well as the reverse driving ratio. It is engaged also duringmanual low operation to effect a bypass around the overrunning clutch100 during engine braking.

Sun gear 50 acts as a reaction member during overdrive operation. It isbraked by overdrive brake band 92 which is applied during fourth ratiooperation. Low and intermediate brake band 64 is applied duringoperation in low and intermediate operation.

In the chart of FIG. 2 the clutch engagement and release pattern isindicated. A symbol "X" is used to define an engaged clutch or brake.The symbol O/R is used to indicate an overrunning condition for theappropriate overrunning clutch.

In the control system shown in FIGS. 4A through 4D the valves and theclutch and brake servos are supplied with fluid pressure developed by apositive displacement pump 38 having a variable displacementcharacteristic. Pump 38 communicates at its outlet side with a highpressure supply passage 102 and it communicates at its low pressureinlet side with a transmission sump 104. The pump 38 includes a statorring 106 which is pivoted at 108 to provide a variable displacementcontrol. The angle to which the stator 106 ring is adjusted with respectto the pivot 108 is dependent upon the pressure supplied to one side ofthe stator ring through a pump control passage 110. The force created bythe pressure in passage 110 is opposed by compression spring 112. For afurther understanding of the mode of operation of variable displacementpumps of this kind, reference may be made to U.S. Pat. No. 3,656,869issued to Alan S. Leonard and to U.S. Pat. No. 4,342,545 issued to DavidA. Schuster.

High pressure line pressure passage 102 supplies line pressure to a mainregulator and boost valve assembly 114 which regulates the pressure to acalibrated value as will be explained subsequently. The output pressureof the main regulator and boost valve 114 is supplied through passage102 to a manual valve assembly 116, which is under the control of thevehicle operator and which permits the operator to select any one ofseveral operating modes. These operating modes are identified in FIG. 4Aby the symbols L, D, OD, N and R which designate, respectively, themanual valve positions for low or manual drive mode, the three speedautomatic drive range mode, the four speed overdrive range mode, neutralcondition and reverse drive.

The manual valve 116, as explained subsequently, delivers workingpressure to the three shift valves that control the ratio changes. Theseare the 1-2 shift and 1-2 throttle delay valve assembly 118 shown inFIG. 4C, the 2-3 shift and TV modulator valve assembly 120 for 2-3shifts and 3-2 shifts shown in FIG. 4C, the 3-4 shift and modulatorvalve assembly 122 for 3-4 shifts and 4-3 shifts and the vehicle speedgovernor assembly 124 shown in FIG. 4C. High pressure is supplied bypassage 102 also to an accumulator regulator valve assembly 126. Valveassembly 126 provides a cushioned engagement of the overdrive brake B₁on a 3-4 upshift. It provides a relatively steep linear relationship ofpressure in the overdrive brake with respect to time and a correspondingrelationship for the rate of pressure build up in the intermediateclutch CL₂. Valve assembly 126 controls also the engagement of theintermediate clutch CL₂ on a 1-2 upshift.

The bypass clutch control valve assembly 128 is supplied with controlpressure from a passage 102 as seen in FIG. 4A. The bypass clutchcontrol regulates the engagement and release of the lockup clutch 28seen schematically in FIG. 1. The function of the bypass clutch controlwill be described particularly later in this specification.

For a particular description of a governor capable of functioning withthe characteristic of governor 124, reference may be made to U.S. Pat.No. 4,323,093 issued to Douglas A. Whitney and U.S. Pat. No. 3,559,667issued to Erkki A. Kolvunen.

In FIG. 4B there is shown a TV modulator and 4-3 scheduling valveassembly 130. Line pressure is distributed to the valve assembly 128through line pressure passage 132 which communicates with passage 134shown in FIGS. 4A and 4C. Passage 134 in turn is supplied with linepressure by the manual valve assembly 116 when the manual valve assemblyis in a condition for overdrive operation corresponding to position OD,when it is positioned for automatic drive range position correspondingto manual valve position D and when it is conditioned for manual-lowoperation corresponding to manual valve position L.

A throttle plunger and control valve assembly 136, shown in FIG. 4A, issupplied with fluid from line pressure passage 102 through passage 138.Output pressure from the throttle plunger and control valve assembly 136delivers a throttle valve pressure signal to passage 140, which extendsto the previously described TV line modulator and 4-3 scheduling valveassembly 130. The output of valve assembly 130 is distributed to passage142 which extends to the 1-2 shift and 1-2 throttle delay valve assembly118 for delaying 1-2 upshifts, to the 2-3 shift and throttle valvepressure modulator valve assembly 120 for delaying 2-3 upshifts and tothe 3-4 shift and TV modulator valve assembly 122 for delaying 3-4upshifts.

Each valve assembly discussed in the foregoing description now will bedescribed with more detail.

MANUAL VALVE ASSEMBLY

Valve assembly 116 comprises a multiple land valve spool 144 havingspaced valve lands 146, 148 and 150. Valve spool 144 is positioned in avalve chamber 152 which is provided with internal valve lands thatregister with the external valve lands of the valve spool. Valve plunger144 can be positioned axially with respect to the internal valve landsin any one of the positions indicated by the symbols L, D, OD and R. InFIG. 4A valve spool 144 is shown in the neutral position N.

When the manual valve spool 144 is positioned as shown, distribution ofpressure from the supply passage 102 to the various valve ports isblocked by lands 146 and 148. When the valve spool 144 is positioned inthe reverse position R, communication is established between supplypassage 102 and reverse line pressure passage 154 as fluid pressure isdistributed across land 148, which registers with axially elongatedvalve groove 157. The pressure in passage 154 causes double positioncheck valve 156 to shift to its right hand position establishingcommunication between passage 154 and forward clutch CL₁. Pressure istransferred also from passage 154 to the reverse clutch CL₄ throughpassage 158 and passage 160. Passage 158 and 160 are parallel. Passage160 is provided with an orifice 162 which is thermostatically controlledso that it is less restrictive when the transmission fluid is cold andmore restrictive when it is hot. A parallel orifice 164 in passage 158is a fixed size orifice. Thus the engagement time for the reverse clutchCL₄ is not unduly prolonged because of low temperature of the oil. Whenthe clutch CL₄ is applied, one-way check valve 164 closes therebypreventing rapid filling of the servo for the reverse clutch. When theclutch is released, however, passage 158 communicates with the reverseclutch through the one-way check valve 164, thereby permitting rapidexhaust of the clutch CL₄ through passage 158 and through the right handend of the manual valve chamber 152, which is open to the transmissionsump.

If the manual valve spool 144 is shifted to the position OD, passage 102communicates with passage 134 through the portion of the valve chamber152 intermediate lands 146 and 148. Passage 134, as mentionedpreviously, communicates with passage 132, which in turn communicateswith passage 166 leading to the 1-2 shift and 1-2 throttle delay valveassembly 118.

When the manual valve is moved to the D position, passage 134 continuesto be pressurized through the same pressure delivery route. Passage 154continues to be exhausted through the right hand end of the valve chamer152. Land 146 moves to the left hand side of port 166 therebyestablishing communication between passage 102 and passage 168. Sincepassage 154 is exhausted, the double position check valve 156 shifts toits left hand

position and the forward clutch CL₁ communicates with passage 170.Passage 168 communicates with passage 170 to pressurize the clutch CL₁.That communication is established by one-way check valve 172. Thus thefront clutch can be engaged with valve assembly 116 in the D positionduring operation in the low ratio, the second ratio and the third ratio.

When the manual valve is shifted to the L position, land 146 on themanual valve spool 144 moves to the left hand side of the port 174 sothat passage 176 becomes pressurized. Both passages 166 and 176communicate with the supply passage 102 through the space in the valvechamber 152 between the lands 146 and 148. Passage 134 also continues tobe pressurized since it too communicates with that same valve space.

1-2 SHIFT AND 1-2 THROTTLE DELAY VALVE

FIG. 4C shows the 1-2 shift and 1-2 throttle delay valve 118 which is incommunication with passage 166. That passage is supplied with controlpressure from the pump 38. Valve assembly 118 comprises a valve spool178 having spaced valve lands 180, 182, 184 and 186. Valve spool 178 issituated in a valve chamber 188 that is occupied also by the throttledelay valve spool 190. Valve spring 192 separates the spools 190 and178, the valve spools being aligned, one with respect to the other.

Valve spool 190 has valve lands 194 and 196 of differential area. Thedifferential area defined by these lands is subjected to throttle valvelimited pressure in passage 198 which communicates with the previouslydescribed throttle valve limited pressure passage 142. Throttle valvespool 190 has a third valve land 200 which is larger in diameter thanland 196. It defines with land 196 a differential area that communicateswith passage 202, which is subjected to a kickdown pressure passage fromthe 2-1 scheduling valve assembly 204.

Line pressure from passage 176 is fed to the valve assembly 204 throughpassage 206. That pressure is regulated by the 2-1 scheduling valve toproduce a 2-1 downshift scheduled pressure in passage 208 which isdistributed to the left hand side of the 1-2 delay valve spool land 194.The pressure in passage 202 or in passage 208 has the effect ofincreasing the effective force of spring 192 thereby increasing the 1-2shift delay during acceleration from a standing start.

Throttle valve limiting pressure is distributed to the differential areaof 2-1 scheduling valve lands 210 and 212 formed on 2-1 sc eduling valvespool 214. That throttle valve limiting pressure is distributed to the2-1 scheduling valve through passage 216 which communicates with passage142. The kickdown pressure that is distributed to passage 202 isreceived from kickdown pressure passage 218 which extends to kickdownpressure port 220 of the throttle plunger and control valve assembly136. The force of the kickdown pressure and the throttle valve limitingpressure on the 2-1 scheduling valve is opposed by valve spring 222 sothat the effective pressure in scheduling pressure passage 208 is afunction of throttle position so that the 2-1 shift point can becontrolled.

The right hand end of land 180 of the 1-2 shift and 1-2 throttle delayvalve assembly 118 is subjected to governor pressure distributed to theassembly 118 through governor passage 232. The magnitude of the pressurein passage 224 depends on vehicle speed.

When the valve spool 178 is in its right hand position, line pressurefrom passage 166 is blocked by the land 184. The valve spool establishescommunication, however, between passages 224 and 226 as the portcommunicating with passage 224 becomes uncovered by land 184. Passage226 under these conditions communicates through the one way check valve228 with passage 230, which in turn communicates with passage 170. Sincepassage 224 thus becomes pressurized, control pressure is distributed tothe forward clutch speed passage 230 through the check valve 228 andthrough the double position check valve 156 located in passage 170. Linepressure, which is present in passage 134, is distributed to passage 132and to passage 234 as seen in FIG. 4D. Communication is established bythe 2-3 servo regulator valve assembly 236 with low-and-intermediateservo apply passage 238 which extends the low-and-intermediate servo B₂as seen in FIG. 4C. Thus when the 1-2 shift and 1-2. throttle delayassembly 118 is in a right hand position, both forward clutch CL₁ andlow-and-intermediate servo B₂ are applied. As indicated in FIG. 2, thiseffects a low speed drive mode.

When the governor pressure in passage 232 increases, the force acting onthe right hand end of the valve spool 178 overcomes the force of spring192 and the force of the throttle valve limiting pressure acting on thevalve spool 190, thereby causing the valve assembly 118 to upshift tothe second drive mode position as spool 178 shifts in a left handdirection. At that time line pressure passage 166 communicates withintermediate clutch feed passage 240. The line pressure signal then isdelivered to port 242 of the main regulator and boost valve assembly114, as seen in FIG. 4A, to effect a cutback in the magnitude of theline pressure maintained by the main regulator and boost valve assembly.The pressure in passage 240 is distributed also to intermediate clutchfeed passage 244, which communicates with feed passage 248 for the 1-2accumulator capacity modulator valve assembly 246 seen in FIG. 4B. Theintermediate 30 clutch CL₂ thus becomes applied as clutch CL₁ continuesto be applied notwithstanding the communication established between feedpassage 226 and exhaust port 250 of the 1-2 shift and 1-2 throttle delayvalve assembly 118.

Passage 224 is pressurized by reason of the communication between linepressure passage 132 and passage 252 through the 3-4 shift and modulatorvalve assembly 122. Passage 252 communicates with passage 224 and withpassage 254 which extends to the forward clutch feed passage 230. Checkvalve 228 closes since passage 226 is exhausted as does one way checkvalve 256.

Passage 240, which becomes pressurized on a 1-2 upshift as explainedpreviously, communicates with exhaust port 257 and the valve assembly118 when the valve 178 is in a right hand position.

2-3 SHIFT AND TV MODULATOR VALVE ASSEMBLY

Valve assembly 120 comprises a multiple land valve spool 258. It isslidably positioned in a valve chamber 260, which has internal valvelands that register with five valve spool lands identified by referencenumerals 262, 264, 266, 268 and 270. Governor pressure from passage 232is distributed to the right hand side of valve land 262. When the valveassembly in the downshift position, the force of valve spring 272 andthe other hydraulic forces acting on the valve spool 258 overcome theforce of the governor pressure in passage 232 and valve spool 258assumes a right hand position, which corresponds to the intermediatespeed ratio. At this time communication is established between linepressure passage 134 and passage 274, which communicates with the lefthand side of the 2-3 servo regulator valve shown at 236 in FIG. 4D. Thisforce supplements the force of valve spring 276 acting on valve spool278 of the valve assembly 236.

The 2-3 servo regulator valve assembly comprises a small valve land 280and larger diameter valve lands 282 and 284. Passage 274, which ispressurized when the manual valve is in the low range position or whenthe shift valves are in the first or second speed ratio positions,distributes pressure to the left hand side of the land 280 to augmentthe force of the spring 276 thus assuring that the valve spool 278 is ina right hand position. This establishes direct communication betweenpassage 234 and the low-and-intermediate speed ratio apply servo feedpassage 238. The 2-3 shift valve spool 258 is shifted in a left handdirection. Upon a 2-3 upshift, however, passage 274 becomes exhaustedthrough exhaust port 286 in the valve assembly 120. This permits the 2-3servo regulator valve to modulate the pressure in passage 238 andcontrol the rate of release of the low-and-intermediate servo B₂ upon a2-3 upshift.

The left hand side of valve land 288 of the 2-3 modulator valve issubjected to throttle valve limiting pressure distributed to it frompassage 198. A companion valve land 292 is acted upon by valve spring272 for the valve assembly 120. Valve lands 288 and 292 are disposed invalve chamber 294, which is aligned with valve chamber 260 for the valveassembly 120. Valve spool 290 on which the lands 288 and 296 are formedmodulates the throttle valve limiting pressure to produce a modified 2-3upshift pressure in crossover passage 296. When the force of governorpressure acting on the right hand side of the shift valve assembly 120overcomes the opposing force of the spring 272 and the modified throttlepressure force in the spring chamber for spring 272, valve spool 258shifts in a left hand direction. This establishes communication betweenline pressure passage 134 and passage 298. Passage 298 in turncommunicates with passage 300, which communicates in turn with passage302 through one way check valve 304 shown in FIG. 4B. Passage 302extends to the release side of the low-and-intermediate servo B.sub. 2.Passage 302 in addition communicates with passage 304, as seen in FIG.4D, and passage 304 supplies control pressure to the direct clutch CL₃through the double position check valve 306 shown in FIG. 4C. As therelease side of the servo B₂ becomes pressurized, the servo is releasedand fluid is exhausted from the apply side. Simultaneously the directclutch CL₃ is applied as clutches CL₁ and CL₂ remain applied. Thus thetransmission is conditioned for direct drive, third speed ratiooperation.

3-4 SHIFT AND MODULATOR VALVE ASSEMBLY

The 3-4 upshifts and the 3-4 downshifts are controlled by valve assembly122. This valve assembly comprises a valve spool 308 which has formedthereon spaced valve lands 310, 312, 314, 316 and 318. Governor pressureis distributed to the right hand side of the valve land 318 throughgovernor pressure passage 320 which communicates with governor pressurepassage 232. Valve spool 308 is positioned in a valve chamber 322 whichhas internal valve lands that register with the lands 310, 312, 314, 316and 318. Aligned with the chamber 322 is a modulator valve chaxber 324which receives valve spool 326. Throttle valve limiting pressure acts onthe left hand side of valve land 328 for the valve spool 326. A secondvalve land 330 on the spool 326 and third land 332 form an area that issubjected to the pressure in passage 352, which is pressurized when thevalve system is conditioned for full range operation in first, second orthird speed ratio. The space between lands 328 and 326 is exhausted.Valve spool 326 modulates the pressure in the throttle valve limitingpressure passage 216 and the modified shift delay signal then isdistributed to the left hand side of the valve spool 308 throughcrossover passage 334.

When the valve assembly 122 is in the upshift position, spool 308 is ina right hand direction thereby establishing communication betweenpassage 252 and passage 132 as explained previously. When the force ofthe governor pressure in passage 320 is sufficient to overcome theopposing force of the spring 336 acting on the left hand side of thespool 308 and the opposing hydraulic forces on the modulator valve spool326. The spool 308 will shift in a left hand direction which correspondsto the upshift condition. This exhausts passage 252 through passage 338in the valve assembly 122. The forward clutch CL₁ thus becomes exhaustedthrough the exhaust passage that now is defined by passage 170, passage254, passage 252 and exhaust port 338. Passage 298, which is fed frompassage 134 through the 2-3 shift valve, now communicates with passage340 through the upshifted 3-4 shift valve assembly 122 as land 312uncovers a port in the assembly 122 that communicates with passage 298.

Passage 340 communicates with overdrive servo feed passage 342, shown inFIG. 4B. The flow path to the overdrive servo includes orifice 344, thusdelaying the rate of application of the overdrive brake. A one way checkvalve 346 in parallel with the orifice 344 permits rapid flow of fluidfrom the overdrive servo as a 4-3 downshift occurs. The exhaust flowpath at that time includes the passage 340 and the exhaust port 348 inthe valve assembly 122.

2-4 INHIBITER VALVE

Inhibiter valve assembly 350 shown in FIG. 4D controls upshifts from thesecond drive range directly to the overdrive range. It is effective toprevent or to inhibit such an upshift until the direct clutch pressurein passage 304 is sufficiently high to accommodate the torquerequirements of the driveline. In this way the friction elements of thedirect clutch CL₃ are protected from excessive energy dissipation andwear if the driving conditions are such that a 2-4 upshift isappropriate.

During operation in the first and second driving ratio, the directclutch CL₃ is released. Thus the pressure in passage 304 is exhausted.Line pressure from passage 132 is applied to the right hand side ofvalve land 352 of the inhibiter valve assembly 350. Valve assembly 350comprises valve spool 354 on which the land 352 is formed in spacedrelationship with respect to companion land 356. Passage 358 extendsfrom the valve chamber 360 for the valve assembly 350 at a locationintermediate the lands 356 and 352 and extends to the valve chamber forthe 3-4 modulator valve assembly and to the valve chaxber 322 for the3-4 shift valve spool 308.

In those circumstances when the upshift from the second ratio to thefourth ratio is called upon, the throttle valve limiting pressure isrelatively low and the valve spool 326 is shifted in a left handdirection. Communication then is established between passage 358 and thespring chamber for spring 336 between the valve spools 326 and 308. Thepressure in passage 358 then forces the 3-4 shift valve spool 308 tomaintain the third speed ratio position. When the clutch pressure inclutch CL₃ increases sufficiently, the pressure in passage 304, which isdistributed to the left hand side of the valve land 356 through passage361, will force the valve spool 354 in a right hand direction. This willallow passage 358 to be exhausted through the 3-4 inhibiter valve andthrough passage 362 and the 4-3 scheduling valve assembly shown at 130.Passage 364, which communicates with the valve assembly 130, serves asan exhaust passage under these conditions since it communicates with theopen end of the manual valve assembly 116. Thus an upshift to the fourthratio can be achieved without experiencing the problems associated withpartial engagement of the clutch CL₃ due to insufficient clutchpressure.

3-2 CONTROL VALVE

Valve assembly 368 is a 3-2 control valve that controls the timing ofthe application of the intermediate servo B₃ and the release of thedirect clutch CL₃ on a 3-2 downshift. Application of the intermediateservo B₂ is achieved by controlling the rate of displacement of fluidfrom the release side of the servo through passage 302 on a 3-2downshift. Fluid pressure must be discharged from the direct clutch CL₃and the release side of the intermediate servo B₂ through passages 302and 304, respectively. Both of these passages 302 and 304 communicatewith a common exhaust flow path on the downstream side of the juncturepoint 370 shown in FIG. 4D. To reach the juncture point 370 the fluiddischarged from the release side of the servo B₂ must pass through flowrestricting orifice 372. The balance of that fluid passes through the3-2 control valve.

The 3-2 control valve comprises a valve spool 374 having three spacedlands 376, 378 and 380. A differential area is defined by the lands 378and 380 and that area is in communication with governor pressure passage332 through governor passage 382. The force of the governor pressure onthat differential area opposes the force of valve spring 384 whichnormally urges the valve spool 374 in a left hand direction. An increasein governor pressure will progressively restrict communication betweenpassage 302 and exhaust flow passage 386. The 3-2 control valve thusacts as a regulator valve as fluid on the downstream side of the 3-2control valve is distributed to the left hand side of the valve spool374 through feedback passage 388. At high vehicle speeds the governorpressure is sufficient to provide a relatively high restriction in theservo release flow path.

The exhaust flow path for the direct drive clutch and the release sideof the servo B₂ on a 3-2 downshift includes passage 302 and orifice 390,one way check valve 392, passage 298, the 2-3 shift valve spool 258,passage 394 which communicates with the 2-3 shift valve chamber 260 andbackout valve assembly 396. The backout valve assembly has a valve spool398 that assumes a right hand position.

TV LIMIT AND NEUTRAL-TO-DIRECT VALVE ASSEMBLY

FIG. 4D shows at 402 a TV limit and neutral-to-direct engagement valveassembly. It includes a TV limit valve spool 404 and a neutral-to-directengagement valve spool 406. Valve spool 406 comprises lands 408 and 410that define a differential area that is in communication with throttlevalve pressure passage 412 which communicates with the previouslydescribed throttle pressure passage 140 described with reference to FIG.4A. Valve spring 414 urges the valve spool 406 in a left hand direction.At low throttle valve pressures spool 406 is stroked in a left handdirection thereby interrupting communication between passage 132, whichis the main line pressure supply passage, and branch passage 416extending to passage 234. Passage 234 communicates with passage 238which supplies the apply side of the low speed servo B₂ through the 2-3servo regulator valve. All of the fluid distributed from passage 132 tothe apply side of the brake servo B₂ then must pass through flowrestricting orifice 418, which bypasses the passage 416. When thevehicle is operated under torque, the TV pressure is sufficiently highto shift the valve spool 406 in a right hand direction therebyestablishing communication between passages 132 and 234.

Located in axial alignment with the valve spool 406 is valve spool 404,which has three spaced lands 420, 422 and 424. Valve spring 426 urgesthe spool 404 in a left hand direction. When the valve spool 406 assumesthe left hand direction, free communication is established betweenthrottle pressure passage 412 and throttle valve limiting pressurepassage 430, which communicates with throttle limiting pressure passage142 described previously. Feedback passage 432 distributed the pressurein passage 430 to the left hand side of the land 420. An exhaust port islocated at 434. The TV limit valve assembly, therefore, is capable ofreducing the magnitude of the pressure developed by the throttle valvein passage 412 and provides a calibrated throttle valve limitingpressure in passage 430, which is distributed to the left hand end ofeach of the three shift valves described previously with reference toFIGS. 4C and 4D. This establishes the shift point for the various ratiochanges. Shift points thus can be calibrated independently of the valueof the throttle valve pressure in passage 412 that is required tomaintain the proper regulated line pressure for the control circuitry.

THROTTLE VALVE ASSEMBLY

The throttle plunger and control valve assembly 136 comprises a valvesleeve 436 having internal lands that register with external lands onthrottle valve spool 438. The lands for the valve spool 438 are shown at440, 442 and 444. Valve spool 438 is urged in a left hand direction asseen in FIG. 4A by valve spring 446.

A throttle valve plunger 448 is arranged in axial alignment with thespool 438 and is separated from the spool 438 by valve spring 444. Foran understanding of the mode of operation of a valve of this kind,reference may be made to U.S. Pat. No. 4,369,677, issued to Charles W.Lewis.

Plunger 448 has spaced lands 450 and 452 which define a differentialarea that communicates with throttle valve limiting passage 442 whichestablishes a force that augments the driver operated linkage forceacting in a left hand direction on the plunger 448. The driver operatedlinkage is connected to the engine carburetor throttle for the internalcombustion engine so that upon movement of the engine caburetor throttleto an open position the spring 446 becomes compressed.

Regulated line pressure from passage 202 is distributed to the valveassembly 136 through port 454. A throttle valve feedback passage 456communicates with the differential area defined by lands 440 and 442.Thus the pressure in passage 140 is a pressure that is proportional tomovement of the plunger 448 and hence it is proportional to the degreeof opening of the engine carburetor throttle. In this respect it isgenerally proportional to engine torque.

MAIN REGULATOR AND BOOST VALVE ASSEMBLY

The valve assembly 114 shown in FIG. 4A regulates the pressure madeavailable to the circuit by the pump 38. It includes a regulating valvespool 458 that has four lands 460, 462, 464 and 466. The output pressurepassage 102 for the pump 38 communicates with the valve chamber thatoccupied by the valve spool 458. Feedback pressure passage 468 extendsto the right hand side of the land 466.

Concentric valve springs 470 act on the left hand end of valve spool458. The innermost spring of the concentric springs acts on a boostvalve element 472 received in a sleeve 474. The left hand end of thespool 472 receives a modified throttle valve pressure from passage 476which communicates with passage 478 through one way check valve 480.Passage 478 thus has a pressure that is generally related in magnitudeto the engine torque, and upon an increase in torque the effective forcethat augments the force of springs of 470 increases to cause an increasein regulated line pressure maintained by the valve assembly 114. Boostvalve element 472 includes also a differential area defined by spacedlands 480 and 482 which communicates with reverse line pressure passage484. Passage 484 communicates with the reverse clutch. Thus whenever thereverse clutch is applied pressure is distributed to that differentialarea to augment the force acting on valve spool 458 in a right handdirection to further increase the magnitude of the circuit pressurelevel during reverse drive.

A pump control pressure passage 486 communicates with the valve chaxberfor spool 458 adjacent land 460. That pressure is distributed to controlchamber 488 in the variable displacement pump 338 thereby causingpivoting movement of the valve stator ring 106 about the pivot 108 todecrease the displacement of the pump and thereby maintain an upperlimit on the magnitude of the regulated line pressure. Lubricationpressure passage 490 communicates with the valve chamber for the valvespool 458 intermediate lands 462 and 464 whereby the magnitude of thelube pressure in passage 490 is maintained at a desired level.

The differential area defined by lands 464 and 466, as previouslymentioned, is in communication with passage 240, as explainedpreviously, through port 242. But that port 242 is exhausted during lowspeed ratio operation as the 1-2 shift valve spool 178 moves to thedownshift position. Thus a higher regulated line pressure is maintainedduring low speed ratio operation that during operation in the second,third or fourth speed ratio. The clutch and brake servos are thuseffective to accommodate the higher torque capacity required for lowspeed ratio operation.

TV LINE MODULATOR AND 4-3 SCHEDULING VALVE

The valve assembly 130 includes a 4-3 scheduling valve spool 492 as seenin FIG. 4B. Spool 492 is located in a valve chamber 494 which is commonto the valve chamber 496 for the TV line modulator valve spool 498.

Valve spool 492 has spaced lands 500, 502 and 504. Passage 364 serves asan exhaust passage since it is exhausted through the end of the manualvalve assembly 116 in all positions except the D and L positions. Valvechamber 492 receives control pressure through the main control pressurepassage 132 adjacent land 500. Passage 506 is the output pressurepassage for the 4-3 scheduling valve. It receives from the 4-3scheduling valve a reduced regulated pressure, the magnitude of which isthe function of the rate of spring 508 acting on the valve spool 492 ina right hand direction as seen in FIG. 4B. Passage 506 distributes thatregulated reduced pressure when the valve system is conditioned forfirst, second or third ratio operation to passage 362 and through the2-4 inhibitor valve assembly 350, to passage 358 and the 3-4 modulatorvalve chamber 324. It thus develops a 4-3 shift point controllingpressure on the left hand side of the land 310 of the 3-4 shift valvespool.

When the transmission is in condition for third speed ratio operation,passage 508 is pressurized because it communicates with passage 252 thatis pressurized when the 3-4 shift valve spool 308 is in the downshiftposition. This introduces a pressure force on the differential area ofland 502 and 504 thereby modifying the effective regulated reducedpressure in passage 506 and establishing the proper 4-3 downshift point.

The throttle valve line pressure modulator valve spool 498 compriseslands 510, 512 and 514. Valve spool 8 is urged in a left hand directionby valve spring 516.

The TV line modulator valve is a regulator valve the exhaust port forwhich is shown at 518. The supply passage for the TV line modulatorvalve is the throttle valve limiting pressure passage 520, whichcommunicates with the previously described passage 430. Valve lands 512and 514 define a differential area that is acted upon by the throttlevalve limiting pressure in passage 520. That pressure augments the forceof the spring 516. The output pressure passage for the TV line modulatorvalve is passage 522 and a feedback branch passage 524 extends from theline 522 to the left hand end of the modulator valve spool 496. Thethrottle valve limiting pressure passage 522 extends to the passage 476as explained previously which in turn communicates with passage 478 andthe left hand end of the main regulator boost valve element 472. The TVline modulator valve in conjunction with the TV limit valve 434 iseffective to distribute a regulator valve modifier pressure that enablesthe main regulator valve to develop a variable control pressure in thecircuit that generally matches the characteristic shape of the enginespeed torque curve for the engine with which the transmission iscalibrated. The internal combustion engine characteristically has acurve similar to that shown, for example, in FIG. 4E.

The relationship between engine carburetor throttle opening and themagnitude of the throttle valve pressure in passage 140 and in passage412 is generally linear as indicated in FIG. 4F. At zero engine throttlethe throttle valve pressure in a typical installation is about 15 psi.At wide open throttle a typical value for throttle valve pressure is 115psi.

Throttle valve pressure is distributed to the TV limit valve throughpassage 412. The TV limit valve is in a left hand position because ofthe spring force of spring 428 when the throttle valve pressure is in arange of values between 15 psi and about 85 psi. Thus the output of theTV limit valve assembly 402 which is distributed to passage 430, islinear just as the throttle valve characteristic of FIG. 4F is linear.The relationship between throttle valve limiting pressure and throttleopening for the engine is indicated in FIG. 4G.

As indicated in FIG. 4D, throttle valve limiting pressure is applied tothe throttle valve line modulator valve assembly 300 and it acts on thedifferential area of lands 512 and 514. This causes the valve spool 498to modulate the pressure in passage 142 to produce a modified throttlevalve limiting pressure in passage 476 which is distributed, asexplained previously, to the left hand side of the boost valve element572 of the main regulator valve 114.

When engine throttle opening is plotted against throttle valve limitingmodulated pressure, a relationship such as that shown in FIG. 4H isdeveloped. Since initially the throttle valve limiting pressure equalsthrottle valve pressure, the portion of the curve shown at 528 is astraight line that generally is parallel to the throttle valve pressureline of FIG. 5F. When a throttle valve modulated pressure of about 30psi is achieved, spring 508 begins to be compressed so that the throttlevalve limiting pressure no longer equals the pressure in passage 522.The effective characteristic curve changes slope at this point asindicated in FIG. 4H. The change in slope is designated by point "X" inFIG. 4H. A further increase in the throttle valve modulated pressurecontinues along straight line portion 530 of the curve of FIG. 4H untilpoint "Y" is reached at which time the throttle valve limit valve spool404 begins to regulate throttle valve pressure as the spring 428 iscompressed. This produces the brake point shown at point "Y" in FIG. 4Hand thereafter the relationship between throttle valve modulatedpressure and engine throttle opening is generally horizontal as shown bycurve portion 532 until the wide open throttle position is reached. Itmay be seen that the curve of FIG. 4H generally approximates the enginetorque curve of FIG. 4E. Thus the main regulator valve is capable ofdeveloping a circuit pressure that generally is related to the magnitudeof the engine torque at any given speed.

BYPASS CLUTCH CONTROL AND CONVERTER REGULATOR

The converter lockup clutch is controlled by a bypass clutch controlshown in FIG. 4A. It includes a multiple land valve spool 530. Fourvalve lands are formed on the valve spool 530 as shown at 532, 534, 536and 538. Valve spool 530 is slidably positioned in valve chaxber 540which has internal valve lands that register with the lands 532, 530,534, 536 and 538.

The bypass clutch control is fed with regulated pressure from the mainregulator and boost valve assembly 114 through passage 542, whichcommunicates with the main regulator valve at a location intermediatelands 462 and 464. An exhaust port 544 registers with the main regulatorvalve chaxber, and a feedback branch passage 546 for the main regulatorvalve spool supplies the feedback pressure that opposes the force of thespring 470. Thus a calibrated pressure is obtained in passage 486 forpump displacement control purposes and a converter feed pressure inpassage 542 is a separately regulated pressure. Passage 542 communicateswith passage 548 across orifice 550.

The feed passage 552 for the converter power inlet communicates withpassage 548 across orifice 554. The converter flow return passage fromthe turbine side of the converter is shown at 556. Flow control orifice558 connects passage 556 with the front lubrication circuit 560. A lubepressure check valve 562 is located in the passage 560. The outlet sideof the valve 562 is connected to the transmission cooler 564 whichsupplies the front lube circuit 566.

When the converter bypass clutch is disengaged, the valve spool 530 ofthe bypass clutch control is in a right hand position which establishesa connection between passage 556 and passage 560 as land 538 uncoversthe valve port in chamber 540 that is connected to passage 560. Thiseffectively bypasses the orifice 558.

In the clutch release position described above land 534 uncovers theport in valve chaxber 540 that communicates with branch passage 568thereby establishing communication between passage 548 and converterbypass flow passage 570 through the branch passage 568.

The converter bypass clutch 28 includes a clutch diaphragm 570 extendingin a radial direction. It cooperates with impeller housing 572 to definea radial outflow passage connecting the passage 570 with the interior ofthe torus circuit. Thus when the clutch is disengaged both passages 552and the clutch bypass passage 570 act as converter flow inlet passageswhile passage 556 serves as a flow return passage.

Control pressure distributed to the left hand end of valve plug 574 frompassage 102 establishes a pressure force on a plug which is transmittedto the valve spool 530 to lock it in the unclutched position. If acontrol signal is distributed to the solenoid pressure line 576,pressure is distributed to the right hand end of land 538 which causesthe valve spool 530 to shift in a left hand direction, which correspondsto the locked clutch condition. The valve port which communicates withpassage 548 then is uncovered by land 536 and converter pressure fluidthen passes from passage 542 through the orifice 550 and through thecompanion orifice 578 to the passage 580, which extends to the cooler564 and the front lube circuit 566. Simultaneously, the portcommunicating with branch passage 568 is brought into communication withpassage 582. Bypass pressure passage 570 is brought into communicationwith exhaust passage 584, which communicates with the exhaust end of themanual valve assembly. The converter feed path then includes passage548, passage 568, passage 582 and passage 552. Passage 556 continues tofunction as a flow return passage from the turbine side of theconverter. All of the fluid returned to the front lube circuit when theclutch is locked must pass through the flow restricting orifice 558. Aback pressure then is developed in the torus circuit which acts on theclutch plate 570 causing the clutch 28 to engage thereby locking theconverter turbine with the converter impeller.

The solenoid pressure in passage 576 is controlled by a converter bypasssolenoid 586, as seen in FIG. 4B. The solenoid is under the control of apower train electronic control module 588 shown in FIG. 3. The moduleestablishes a pulse width modulation characteristic in response to inputsignals to develop a desired pressure in passage 476. The input signalsfor the module 588 may be analog signals representing engine inputspeed, throttle position for the engine carburetor, engine temperature,vehicle speed. A wheel brake signal is used also. It is active when thewheel brakes are applied so that the module will cause the solenoid tobe disabled thereby exhausting the passage 576 and unlocking theconverter when the vehicle is braked. This avoids stalling of the enginewhen the wheel brakes are applied while the transmission is in acruising, converter lockup drive condition. The output from the module588 is a signal used by the on/off bypass solenoid 586 to establish adesired pressure level in passage 576. Governor output indicated in FIG.3 is a self-test diagnostic output signal.

When the signal in passage 576 is above a special value, the bypasscontrol clutch valve element 530 is shifted to a locked condition in aleft hand direction. If the signal in passage 576 is lower than a lowthreshold value, the bypass clutch control valve spool 530 is shiftedfully to its right hand clutch unlocked position. For values of pressurein passage 576 between the upper threshold value and the lower thresholdvalue, a variable pressure in the clutch bypass control circuit isdeveloped which in turn results in a varying clutch capacity for thelockup clutch 28. The clutch capacity can be matched with the optimumclutch capacity that is dictated by any given engine speed throttleposition, engine temperature and vehicle speed.

Passage 590 shown in FIG. 4A is a lube passage that is separate from thefront lube circuit. It is identified in FIG. 4A as a rear lube circuit.The rear lube circuit is fed through orifice 592, which is incommunication with the previously described passage 548. The added lubecapacity for the transmission system made available by the twoindependent lube circuits provides better lubrication and betterdurability since it is not necessary to rely on a single flow paththrough the torque converter to establish lubrication at the varioustransmission lubrication points. One lubrication flow path is from thecooler return circuit and the other is from the converter chargecircuit.

The converter bypass solenoid valve is a normally open valve comprisingorifice 594 and solenoid actuated armature valve element 596. Solenoidorifice 594 is supplied with pressure from passage 302 through filter598 and through flow restricting orifice 600. Passage 302 is pressurizedwhenever the release side of the intermediate servo B₂ is pressurized.This condition exists only during third or fourth speed ratio operation.Thus it is possible for the lockup clutch to be engaged only duringoperation of the driveline in the third or fourth ratio.

The pressure level in the torus circuit of the impeller housing ismaintained at a desired level by converter regulator valve 602 whichcomprises a regulator valve spool 604 with spaced lands 606, 608 and610. Valve spool 604 is urged in a right hand direction by valve spring612. Lands 608 and 610 define a differential area that receives pressurefrom passage 548. The force of that pressure is opposed by spring 612.The exhaust port for valve 602 is shown at 614. The pressure maintainedin passages 548 and 552 is a reduced pressure that is dependent on thespring force and the differential area of lands 608 and 610.

PARTICULAR DESCRIPTION OF THE VALVE CIRCUIT OF FIG. 5

The backout valve 396 has four spaced valve lands on its valve element398, as shown at 616, 618, 620 and 622. Valve element 398 is biased in aright-hand direction, as viewed in FIG. 5, by valve spring 624. Passage298 communicates with the valve chamber for valve 396 at a pointintermediate the lands 616 and 618, the diameter of the land 616 beinglarger than the diameter of land 618. Thus, when the passage 298 ispressurized, the valve element 398 is shifted in a left-hand directionagainst the force of spring 624. The valve element 398 assumes thatposition except during a backout drive mode, which will be explainedsubsequently.

Passage 300 communicates with the valve chamber for backout valve 396adjacent land 618. It is blocked by the land 618 when the valve element398 is shifted in a left-hand direction and communicates with passage298 when the valve element 398 is moved in a right-hand direction.

Passage 340 communicates with the valve chamber for the backout valve396 at a point between lands 618 and 620. Passage 340 is brought intocommunication with passage 626 when the backout valve element 398 isshifted in a right-hand direction causing passage 626 to be uncovered byvalve land 620.

Passage 394 communicates with the backout valve 396 at a pointintermediate lands 620 and 622. When the element 398 is shifted in aleft-hand direction, communication is established between the passage394 and passage 44. When the valve element 398 is shifted in aright-hand direction, passage 394 is exhausted through the exhaust port400 in the backout valve 396.

Backout valve 396 is supplied with backout pressure at its left-hand endthrough backout pressure line 628. When passage 628 is pressurized, aforce is applied to the valve element 398 that supplements the force ofthe spring 624, tending to shift the valve element 398 in a right-handdirection. Passage 628 communicates through two-way check valve assembly631, shown in FIG. 4A, with passage 632 which communicates with theright-hand end of the throttle plunger and control valve, also shown inFIG. 4A.

Under light throttle operating conditions or when the engine is operatedat its idle throttle setting, valve plunger 448 is moved in a right-handdirection so that land 450 on the plunger uncovers passage 632 andcauses passage 632 to be exhausted through the spring chamber for spring446 of the throttle plunger and control valve assembly. Under theseconditions, the backout valve element 398 is stroked in a left-handdirection assuming that the passage 298 is pressurized. On the otherhand, when the throttle valve plunger 448 is moved toward an advancedthrottle position, land 450 uncovers passage 632, thereby establishingcommunication between passage 632 and limited throttle pressure passage142. This causes passage 632 to be subjected to limited throttlepressure, thereby causing valve element 398 to shift when the throttlepressure is sufficient to overcome the opposing hydraulic pressure forceof the pressure in passage 298.

DESCRIPTION OF THE FUNCTION OF THE BACKOUT VALVE

During heavy throttle operation as the vehicle is accelerating from thelowest ratio to the highest ratio, the backout valve is effective tocontrol heavy throttle 2-3 upshifts. Under these conditions passage 628is pressurized, as explained previously, so the valve element 398 isstroked in a right-hand direction. This establishes communicationbetween passage 298 and passage 300.

A flow control orifice 630 is located in passage 300, the downstreamside of the orifice 630 communicating with passage 302 through one-waycheck valve 304. Passage 300 also communicates with the passage 300through a second flow controlling orifice 632. Thus the pressure inpassage 300 is distributed to passage 302 through both orifices 630 and632 when the valve element 398 is stroked in a right hand direction,which would correspond, as explained previously, to a heavy throttle 3-2upshift. Thus when the 2-3 shift valve element 258 is shifted to itsupshift position upon an increase in governor pressure in passage 232,line pressure passage 134 is brought into communication with passage 132thereby pressurizing the latter. That pressure then is distributedthrough passage 298 and through the backout valve assembly 396 to thepassage 300 on the upstream side of the orifice 630. Thus the passage302 is supplied with fluid from both the orifice 630 and the orifice 632under these heavy throttle 2-3 upshift conditions. This delays theapplication of the direct drive clutch and the release of theintermediate servo, the latter being in communication with the directdrive clutch through a common feed passage 304. Passage 304 in turncommunicates with passage 302 at the hydraulic connection point 370.Because of the delay in the full application of the clutch with respectto the release of the brake, the rotating elements of the direct driveclutch will have sufficient time to achieve synchronism thus avoidingundue inertia forces and harshness in the ratio change.

If a 2-3 upshift should occur under closed throttle conditions or underlight throttle conditions, the backout valve pressure in passage 628 isinsufficient to keep the valve element 398 in its right hand position.Thus the valve land 618, upon movement of the valve element 398 in aleft hand direction, will block passage 300. This blocks the feed forthe orifice 630. Thus the passage 300 and the passage 298 communicatewith the clutch feed passage 302 through the single orifice 632. Thisdelays the application of the direct clutch and the release of the lowand intermediate servo B2.

The back-out valve assembly is capable also of controlling a lightthrottle 3-4 upshift as well as a heavy throttle 3-4 upshift so that thetiming of the 3-4 ratio change can be tailored to accommodate the torquerequirements for both heavy throttle and light throttle conditions,thereby making it possible to calibrate the system for maximumsmoothness in the ratio change. Upon a light throttle 3-4 upshift, the3-4 shift valve assembly 122 shifts in a left hand direction. The 3-4shift valve assembly is fed from the 2-3 shift valve assembly which,under these conditions, is in its upshift position. Thus line pressurepassage 134 is in communication with the 3-4 shift valve feed passage298 through the 2-3 shift valve assembly. Passage 298, upon a 3-4upshift, communicates with passage 340 through the 3-4 shift valveassembly as land 312 uncovers the connection with passage 298.

Since passage 298 becomes pressurized in this manner, it feeds theoverdrive servo B1 through orifice 344 and the feed passage 342. Thusall the pressure delivered to the overdrive servo must pass through theorifice 344. Under these conditions land 620 of the backout valve blockspassage 626. On the other hand during a heavy throttle 3-4 upshift thepressure in passage 628 is capable of shifting the valve element 398 ina right hand direction, thereby establishing communication betweenpassage 340 and passage 626. This provides a parallel feed passage tothe overdrive servo since the passage 626 communicates with theoverdrive servo through orifice 345. The overdrive servo then willbecome applied more quickly under heavy throttle 3-4 upshift conditionsthan it would be applied during light throttle 3-4 upshift conditions.Thus the timing of the 3-4 upshift can be controlled to meet the torquerequirements of the driveline for both light throttle conditions andheavy throttle conditions and this control is achieved by the backoutvalve without adding any unique valve elements or significant addedcircuit structure.

The back-out valve also is capable of functioning as a power-on 3-2downshift control when a downshift occurs with intermediate or advancedthrottle settings. Under these conditions backout pressure in passage628 is sufficient to cause the valve element 398 to shift in a righthand direction. This uncovers exhaust port 400 so that passage 394 isexhausted through the backout valve through the exhaust port 400.

The 2-3 shift valve assembly 120 connects passage 298 to passage 394when it assumes the second ratio position. Passage 394 is exhaustedthrough the backout valve exhaust port 400, as explained previously.Passage 298 is connected to the direct clutch CL3 through the passage300, through the check valve 392, orifice 390, passage 302 and passage304, the latter extending to the direct drive clutch CL3 and also to therelease side of the intermediate brake servo B2 through passage 302. Theconnection between passage 302 and passage 304 is shown at 370.

On light throttle 3-2 downshifts, the backout valve element 398 isshifted to the left as the pressure in passage 628 is reduced asexplained previously. When this occurs, the passage 244 becomesconnected to passage 394 through the backout valve assembly, and exhaustport 400 becomes blocked. Passage 394 then becomes pressurized whichdisables the 2-3 shift valve. Thus the 2-3 shift valve is capable ofmoving from its left hand position to its right hand position withouthaving any effect on ratio changes. Passage 394 no longer can beselectively pressurized and exhausted by the 2-3 shift valve since it iscontinuously pressurized by the backout valve assembly. Since thevehicle is coasting down with minimum throttle setting, no ratio changeoccurs upon movement of the 2-3 shift. Rather the downshift iscontrolled by 1-2 shift valve assembly. If the speed during coastingfalls below the shift point value, passage 240 becomes connected to vent258 in the 1-2 shift valve assembly. This causes the intermediate clutchCL2 to become exhausted since the feed passage 248 for the intermediateclutch is connected to the passage 244 through the 1-2 capacitymodulator 246.

The 1-2 accumulator capacity modulator valve 246 comprises a valve spool634 that is biased in an upward direction by valve spring 636. When thevalve spool 634 is shifted upward, communication is established betweenpassage 240 and passage 248 leading to the clutch CL2 as pressure buildsup. The pressure in the clutch CL2 is distributed to the upper end ofthe valve spool 634 thereby progressively restricting the communicationbetween passages 240 and 248. The pressure acting on the lower end ofthe valve spool 634 is the pressure on the downstream side of flowcontrol orifice 638, which is used to stroke the piston 640 of 1-2accumulator 642 against the opposing force of accumulator valve spring644. After the accumulator 642 is stroked fully, flow across the orifice638 no longer occurs and the pressure on the lower side of the valvespool 634 balances the force on the upper end of the valve spool so thatthe valve spool shifts upwardly to its original position.

Having described a preferred embodiment of my invention, what I claimand desire to secure by U.S. Letters Patent is:
 1. In a control systemfor an automatic transmission for an automotive vehicle, saidtransmission having a torque input shaft, a torque output shaft, ahydrokinetic torque converter with an impeller connected to the torqueinput shaft and a turbine, and multiple ratio gearing having an inputelement connected to said turbine and an output element connected tosaid output shaft;first clutch and brake means for controlling therelative motion of the elements of said gearing to establish anddisestablish ratio changes between a fourth speed ratio and a thirdspeed ratio; Second clutch and brake means for controlling the relativemotion of the elements of said gearing to establish and disestablishratio changes between a second speed ratio and said third speed ratio;third clutch and brake means for controlling the relative motion of theelements of said gearing to establish and disestablish ratio changesbetween a first speed ratio and said second speed ratio; fluid pressureactuators for each of said clutch and brake means; a fluid pressurepump; conduit structure connecting said pump and said actuatorsincluding a 1-2 shift valve means for controlling selectivelydistribution of actuating pressure to the actutor for said third clutchand brak means, a 2-3 shift valve means for controlling selectivelydistribution of actuating pressure to the actuator for said secondclutch and brake mans and a 3-4 shift valve means for controllingselectively distibution of actuating pressure to the actuator for saidfirst clutch and brake means; a source of a pressure signal proportionalin magnitude to input torque and a source of a pressure signalproportional in magnitude to output shaft speed; said signal sourcesbeing in communication with said shift vale means; a backout valve meansfor controlling the rate of response of the actuators to shifting ofsaid 2-3 shift vale means to a third speed ratio condition from a secondspeed ratio condition, said backout valve means comprising a backoutvalve element in said conduit structure that is movable from a firstposition to a second position, said torque signal source communicatingwith said backout valve element whereby the latter is urged to itssecond position; flow control orifices in said conduit structurecommunicating with said backout valve means in parallel relationship,one with respect to the other, said orifices being located in thepressure distribution path of said conduit structure position that feedssaid second clutch and brake means; both control orifices beingeffective to control actuator pressure for said second clutch and brakemeans when said backout valve element assumes its second position andone orifice being effective to control actuator pressure for each secondclutch and brake means when said backout valve element assumes its firstposition.
 2. The combination as set forth in claim 1 wherein saidbackout valve means is in the conduit structure portion that feeds thesaid first clutch and brake means, the latter conduit structure portionhaving two orifices in parallel, one of said two orifices communicatingwith a high pressure region of said conduit structure through saidbackout valve means when said backout valve element is in its firstposition and the both of said two orifices communicating with said highpressure region when said backout valve element is in its secondposition.
 3. The combination as set forth in claim 1 wherein saidbackout valve means includes an exhaust port that communicates with said1-2 shift valve means whereby the actuator for said third clutch andbrake means is exhausted through said backout valve means on a ratiochange from the second speed ratio to the first speed ratio undertorque.
 4. The combination as set forth in claim 2 wherein said backoutvalve means includes an exhaust port that communicates with said 1-2shift valve means whereby the actuator for said third clutch and brakemeans is exhausted through said backout valve means on a ratio changefrom the second speed ratio to the first speed ratio under torque. 5.The combination as set forth in claim 3 wherein said 2-3 shift valvemeans includes a pressure supply passage, a pressure delivery passagecommunicating with the actuator for said second clutch and brake meansand an exhaust passage;said backout valve means communicating with saidexhaust passage and being adapted to connect the same to a high pressureregion of said conduit structure when said backout valve element isshifted to its first position whereby said 2-3 shift valve means isdisabled upon a light throttle downshift from the third ratio thuseffecting an automatic ratio change from the third speed ratio directlyto the first speed ratio upon downshifting movement of said 1-2 shiftvalve means.
 6. The combination as set forth in Claim 4 wherein said 2-3shift valve means includes a pressure supply passage, a pressuredelivery passage communicating with the actuator for said second clutchand brake means and an exhaust passage;said backout valve meanscommunicating with said exhaust passage and being adapted to connect thesame to a high pressure region of said conduit structure when saidbackout valve element is shifted to its first position whereby said 2-3shift valve means is disabled upon a light throttle downshift from thethird ratio thus effecting an automatic ratio change from the thirdspeed ratio directly to the first speed ratio upon downshifting movementof said 1-2 shift valve means.